| //! Detecting language items. |
| //! |
| //! Language items are items that represent concepts intrinsic to the language |
| //! itself. Examples are: |
| //! |
| //! * Traits that specify "kinds"; e.g., `Sync`, `Send`. |
| //! * Traits that represent operators; e.g., `Add`, `Sub`, `Index`. |
| //! * Functions called by the compiler itself. |
| |
| use crate::ty::{self, TyCtxt}; |
| |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::LangItem; |
| use rustc_span::Span; |
| use rustc_target::spec::PanicStrategy; |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| /// Returns the `DefId` for a given `LangItem`. |
| /// If not found, fatally aborts compilation. |
| pub fn require_lang_item(&self, lang_item: LangItem, span: Option<Span>) -> DefId { |
| self.lang_items().require(lang_item).unwrap_or_else(|msg| { |
| if let Some(span) = span { |
| self.sess.span_fatal(span, &msg) |
| } else { |
| self.sess.fatal(&msg) |
| } |
| }) |
| } |
| |
| pub fn fn_trait_kind_from_lang_item(&self, id: DefId) -> Option<ty::ClosureKind> { |
| let items = self.lang_items(); |
| match Some(id) { |
| x if x == items.fn_trait() => Some(ty::ClosureKind::Fn), |
| x if x == items.fn_mut_trait() => Some(ty::ClosureKind::FnMut), |
| x if x == items.fn_once_trait() => Some(ty::ClosureKind::FnOnce), |
| _ => None, |
| } |
| } |
| |
| pub fn is_weak_lang_item(&self, item_def_id: DefId) -> bool { |
| self.lang_items().is_weak_lang_item(item_def_id) |
| } |
| } |
| |
| /// Returns `true` if the specified `lang_item` must be present for this |
| /// compilation. |
| /// |
| /// Not all lang items are always required for each compilation, particularly in |
| /// the case of panic=abort. In these situations some lang items are injected by |
| /// crates and don't actually need to be defined in libstd. |
| pub fn required(tcx: TyCtxt<'_>, lang_item: LangItem) -> bool { |
| // If we're not compiling with unwinding, we won't actually need these |
| // symbols. Other panic runtimes ensure that the relevant symbols are |
| // available to link things together, but they're never exercised. |
| match tcx.sess.panic_strategy() { |
| PanicStrategy::Abort => lang_item != LangItem::EhPersonalityLangItem, |
| PanicStrategy::Unwind => true, |
| } |
| } |